Problem: Solve for $x$ : $1 = x - 21$
Solution: Add $21$ to both sides: $ \begin{eqnarray} \\ \hphantom{1 {+ 21}} &\hphantom{=}& \hphantom{x} \\ 1 &=& x - 21 \\ \\ {+21} && {+21} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 1 {+ 21} &=& x \\ \end{eqnarray} $ Simplify. $ x = 22$